Insulin pumps are widely available and are used by diabetic people to automatically deliver insulin over extended periods of time. Many currently available insulin pumps employ a common pumping technology, the syringe pump. In a syringe pump, the plunger of the syringe is advanced by a lead screw that is turned by a precision stepper motor. As the plunger advances, fluid is forced out of the syringe, through a catheter to the patient. The choice of the syringe pump as a pumping technology for insulin pumps is motivated by its ability to precisely deliver the relatively small volume of insulin required by a typical diabetic (about 0.1 to about 1.0 cm3 per day) in a nearly continuous manner. The delivery rate of a syringe pump can also be readily adjusted through a large range to accommodate changing insulin requirements of an individual (e.g., basal rates and bolus doses) by adjusting the stepping rate of the motor. While the syringe pump is unparalleled in its ability to precisely deliver a liquid over a wide range of flow rates and in a nearly continuous manner, such performance comes at a cost. Currently available insulin pumps are complicated and expensive pieces of equipment costing thousands of dollars. This high cost is due primarily to the complexity of the stepper motor and lead screw mechanism. These components also contribute significantly to the overall size and weight of the insulin pump. Additionally, because of their cost, currently available insulin pumps have an intended period of use of up to two years, which necessitates routine maintenance of the device such as recharging the power supply and refilling with insulin. These syringe type pumps, even if described as disposable, are simply too expensive to be truly disposable, or are alternatively disposed at a very high cost to patients and insurance companies alike.
Shape memory alloys are a part of a class of materials that change shape when power is applied to them but that return to their natural state when the power is removed. The materials can be used to form an actuator by harnessing this unique attribute of the materials. A pump can be made with a shape memory alloy actuator. However, a shape memory alloy does not have the inherent accuracy and repeatability of the precision stepper motor used in a syringe pump. Although price is always important, precision is also essential in a pump used to deliver insulin or other drugs. It is therefore necessary to provide a system to precisely control and actuate a pump utilizing a shape memory material as an actuator.